The invention relates to a printing device, in particular, for flexographic printing (flexo printing), comprising a support roll, a sleeve and at least one printing plate to be secured on the sleeve, wherein the sleeve comprised of at least one sleeve element is mountable on the support roll and surrounds the support roll at least partially in the mounted state.
During printing, the support roll and the sleeve form a unitary body of rotation with the sleeve, however, being exchangeable. The sleeve can be first provided with the printing plate and then pushed onto the support roll such that the sleeve is widened at its inner side by compressed air exiting from the support roll and is slidably movable on an air cushion to the desired location (pneumatic threading) before it is seated elastically on the support roll when the compressed air is switched off. Other known detachable securing means for sleeve and support roll provide for positive-locking engagement in the direction of rotation, for example, by means of a tongue and groove connection. In this way, changeover/makeready times for printing can be shortened, different outer sleeve diameters can be provided, and it is possible to axially sequentially position several sleeves on the support roll.
For printing films, paper sheets, or paper webs, at present so-called water-based printing inks, UV printing inks, and solvent printing inks are used, i.e., printing inks that upon removal of water, by irradiation with UV light, or by removal of a (chemical) solvent will dry or set (cure). In this connection, in particular, in the case of flexo printing, a multi-roll system that is referred to as a printing group is used for each printing ink. The outer sides of the usually cylindrical printing group in contact with the material to be printed on are, for example, in the form of printing plates having a flexible bottom and mounted on a sleeve of the printing group. In order for the printing plates not to become detached from the fast-rotating sleeve of the printing or support rolls of the printing group during the printing process, they can be attached in different ways on the sleeves. For this purpose, double-sided adhesive mounting tapes or also foam adhesives are used, for example.
Instead of using adhesive mounting tapes or foam adhesives for attaching printing plates on the sleeve, it is also possible to attach a layer of polymers fixedly on the outer side of the sleeve. After curing of the polymer layer, it is ground to be round and subsequently is laser-engraved in accordance with the printing image to be produced. Both technologies have the disadvantage that they are time-consuming and cost-intensive.
Because of a continuously increasing demand for printing devices, in particular, flexo printing machines, with an ever increasing number of printing groups, there is the need to simplify the application of a printing plate (image to be printed) on a sleeve.